The Cytogenetics Shared Resource provides individual Cancer Center investigators with expertise in the conventional and molecular cytogenetic analyses of human and mouse tumor cell lines, somatic cell lines and tumor tissues, as well as mouse peripheral blood and tail DNA samples. This Resource offers services for conventional (e.g., karyotyping of cell lines) and molecular (e.g., FISH, fiber FISH, quantitative FISH) analyses of cells and tissues that would otherwise be difficult (i.e., expensive), if not impossible, to obtain outside this institution. In addition, services are tailored to meet the needs of individual investigators when and where appropriate. For example, new molecular cytogenetic assays have been incorporated into the core to meet the needs of the investigators within the Solid Malignancy and Molecular Oncology Programs of the Cancer Center. Examples include fiber FISH, or DIRVISH, which is a new application of fluorescence in situ hybridization that utilizes linearized free chromatin as a hybridization target. This technique has the capacity to detect very small changes in the genome (i.e., less than 5 kb), and was recently used to detect deletions within the CASP8 gene in a neuroblastoma cell line with a small homozygous deletion. Quantitative FISH was incorporated into the facility in order to determine the copy number of a BAC transgene within specific transgenic mice for investigators in the Solid Malignancy, Molecular Oncology and Neurobiology and Brain Tumor Programs. This method facilitates the quantitative assessment of copy-number of a BAC transgene when compared with the endogenous gene locus. It has also been used to genotype (heterozygous vs. homozygous) approximately 160 of these transgenic mice by using a novel method of FISH using tail cells as the hybridization target. A FISH assay was recently incorporated into the core facility to analyze the length of telomeres in cell lines derived from various genetically altered mice. The fiber FISH and telomere FISH assays were developed to meet the needs of investigators in the Molecular Oncology, Solid Malignancy, and Hematopoietic Malignancy Programs. The telomere FISH assay is being used to accurately analyze changes in telomere length of chromosomes from tumor cells in a ploidy-independent manner. Recently, this Shared Resource has also added flow FISH to the list of services provided to Cancer Center investigators. Thus far, the Programs in Molecular Oncology, Developmental Therapeutics for Solid Malignancies, Hematopoietic Malignancies, as well as Neurobiology and Brain Tumors, have been able to benefit from the addition of this new methodology. This method has been used to determine the length of telomeres in the peripheral blood cells of patients who have undergone chemotherapy in order to determine the magnitude of the shortening of the telomeres resulting from this treatment. Thus, the Cytogenetics Shared Resource offers not only conventional analysis, but meets the needs of the various investigators within the Cancer Center to continue providing first-rate service that often plays a role in the obtaining of individual RO1 grants, and/or their renewals, for Cancer Center investigators.